This invention relates to tackifiers for rubber and in particular to non-phenolic tackifiers for rubber used in tire building.
A rubber product, such as a tire, is often manufactured from several pieces of vulcanizable rubber compound, commonly referred to as green rubber. The green rubber is typically formed from a polymer, filler, plasticizer, tackifier, process aids, and a vulcanizing agent. The pieces of green rubber are typically pressed together and then inserted into a mold. In the mold, the pieces of green rubber are subjected to heat and pressure to effect curing and formation of the tire. The tackifier is included in the green rubber in order to increase the adherence of the pieces of green rubber to each other, i.e., to increase their tack. If there is insufficient tack between laminated layers of green rubber, air may become trapped between the layers, which is undesirable.
Generally, there are two different types of tackifiers in the rubber industry: hydrocarbon resin tackifiers and phenolic resin tackifiers. Sometimes, blends of hydrocarbon resin tackifiers and phenolic resin tackifiers are used. Hydrocarbon tackifiers provide good initial tack, but typically do not provide good long-term tack. Phenolic tackifiers provide good initial and long-term tack, but are typically expensive. In addition, when pellets of phenolic tackifiers are subjected to heat and humidity for a period of time, the pellets typically join together to form an unwieldy mass. Phenolic tackifiers also contribute to mold fouling, which is a buildup of black sticky residue on the mold. In some cases, phenolic tackifiers will also interfere with the cure of green rubber components.
Based upon the foregoing, there is a need in the art for a tackifier for a rubber compound, wherein the tackifier provides good initial and long-term tack, does not readily mass together, and reduces undesirable side-effects, such as mold fouling. The present invention is directed to such a tackifier and a rubber compound containing the same.